(5cm) Control over the Shape of Nanostructures in Block Copolymer Lithography and Implications for Nanomanufacturing

Current photolithographic materials and processes are capable of producing features at 70 nm length scales with adherence to exacting standards of control over the dimensions and profiles of those features. Presently, it is unclear whether chemically amplified resists, the state of the art in photolithography, will be capable of producing structures within those exacting standards as feature dimensions are extrapolated to sub-30 nm length scales. Although other resist materials, such as calixarene and ZEP, are being explored for patterning at sub-30 nm dimensions, these materials may not be fully amenable to manufacturing processes.

Another promising route to patterning at the nanoscale is directed self-assembly. Diblock copolymers are molecules that consist of two chemically distinct chains covalently bonded at one end. When heated above the glass transition temperatures of the constituent blocks and below an order-disorder transition temperature, diblock copolymers spontaneously microphase separate to form ordered structures including spheres, cylinders and lamellae with characteristic lattice periods on the order of 10 ? 50 nm. When lamellae and cylinder forming diblock copolymers are directed to assemble on chemically nanopatterned substrates with pattern periods, LS, that are commensurate with the bulk repeat period of the block copolymers LO, they are capable of satisfying the essential attributes of the lithographic process at the nanoscale: patterning perfection, substrate registration and the ability to generate non-regular device-oriented structures.

Moreover, we demonstrate that the perfection, registration, dimensions and shape of diblock copolymer domains assembled on chemically nanopatterned substrates is highly tolerant to mismatch between the two dimensional projections of the desired film structure and the dimensions of the chemically patterned areas on the surface. Lamellar domains assembling on chemically striped surfaces with period LS, for example, maintained widths of 0.5 Ls for ratios of the widths of underlying adjacent chemical stripes as mismatched as 1:2. In addition, the angles of the interfaces between domains remained within 10 degrees of the surface normal over the same degree of mismatch. Such control over the shape and the dimensions of the nanostructures is critical for pattern transfer processes.